[The software has been revised since this review was written. The current version number is 8.20. The main change affecting this review is that the original 25-month Goddess Calendar has been replaced by the 12/13-month version.]

This program provides a rich set of functions of interest to anyone doing serious work with the Mayan calendar. It does not provide any interpretive data on the days, just the calculative functions. Anyone who wants to seriously study the Mayan calendar, start thinking in Mayan time, or perform calculations with it, would have an interest in this program.

The program has great flexibility in the settings of the calendar. One can configure the correlation number. The program uses the default of the traditional count, in my opinion the correct one. People in South America whose ancestors followed the Mayan calendar use this number. However others have come up with other correlation numbers and one can pick from a list or put in their own. The program enables one to set the month's base, or seed. Most systems start the month with 0, i.e. 0 Pop. This day "seeds" the month. However others started it at 1. This enables finding equivalent dates between different calendar systems used by various Mayan groups and tribes. The program allows one to set the year-bearers — the daysigns which can begin each new Mayan Haab (solar) year. One can select from two sets of names for the days and months. One can also set the date format for Gregorian dates: European, American, and ISO standard. Output from the program will get inserted at apropos points, starting below. The program provides logging and printing facilities.

Maya and Goddess Calendars (Version 6.22) Copyright 1990-1997 Peter Meyer Correlation number = 584,283 (Thompson) Year bearers: Ik, Manik, Eb, Caban Month base number = 0 Tikal system (Dresden Codex) Date format: American

One can perform many functions once they have the calendar set to their liking, though one will in most cases not need to tweak things much. The calendar will convert easily between Gregorian dates, Julian dates, Mayan long count dates, Mayan Tzolkin (Sacred calendar) dates, and Goddess Calendar dates. The Goddess Calendar is an accurate lunar calendar invented by Peter.

Gregorian = 14 Jul 1977 J.d.n. = 2,443,339 Julian = 1 Jul 1977 C.n. = 584,283 GLC = 11/29/2987 L.c. = 12.18.4.0.16 8 Cib 12 Zec (Yucatan) 8 Cib 13 Zec (Campeche) 8 Cib 14 Zec (Tikal) 8 Cib 13 Zec (Mayapan) 8 Cib 14 Zec (A) 8 Cib 15 Zec (B) Days since 0.0.0.0.0: 1,859,056 L.c. = 12.19.4.15.6 M.d.c. = 1,866,546 Tzolkin/haab: 10 Cimi 4 Muan (Tikal) C.n. = 584,283 Gregorian = 15 Jan 1998 J.d.n. = 2,450,829 Julian = 2 Jan 1998 Lunar = 18 Oya 2997

The program has functions to easily see today's and tomorrow's date.

Today's date is: Gregorian calendar: 01/15/1998 January 15, 1998 Julian calendar: 01/02/1998 January 2, 1998 Goddess Lunar calendar: 2997-15-18 Oya 18, 2997 Julian day number: 2,450,829 Maya tzolkin-haab date: 10 Cimi 4 Muan Tikal system (Dresden Codex) Long count: 12.19.4.15.6 using c.n. 584,283 (Thompson) Days since 0.0.0.0.0: 1,866,546 Tomorrow's date is: Gregorian calendar: 01/16/1998 January 16, 1998 Julian calendar: 01/03/1998 January 3, 1998 Goddess Lunar calendar: 2997-15-19 Oya 19, 2997 Julian day number: 2,450,830 Maya tzolkin-haab date: 11 Manik 5 Muan Tikal system (Dresden Codex) Long count: 12.19.4.15.7 using c.n. 584,283 (Thompson) Days since 0.0.0.0.0: 1,866,547

The Pictun calculator comes in immense handy. It allows calculations using the Mayan long count and extended pictun system.

00.00.00.12.19.04.15.06 -00.00.00.12.18.04.00.16 = 00.00.00.00.01.00.14.10 = 7,490

Since various correlations exist, the program has a unique function to find the correlation number if you know both the Mayan date and Gregorian or Julian date.

Tzolkin/haab: 10 Cimi 4 Muan Assuming this date fell on 01/15/1998 G then: Calendar round position = 6506 First day of this calendar round is JDN 2,444,323, 03/24/1980 G First day of next calendar round is JDN 2,463,303, 03/11/2032 G Possible correlation numbers around 584,283: 508,363 then 0.0.0.0.0 = 10/01/-3321 G and 13.0.0.0.0 = 02/10/1805 G 527,343 then 0.0.0.0.0 = 09/19/-3269 G and 13.0.0.0.0 = 01/28/1857 G 546,323 then 0.0.0.0.0 = 09/06/-3217 G and 13.0.0.0.0 = 01/16/1909 G 565,303 then 0.0.0.0.0 = 08/24/-3165 G and 13.0.0.0.0 = 01/03/1961 G 584,283 then 0.0.0.0.0 = 08/11/-3113 G and 13.0.0.0.0 = 12/21/2012 G 603,263 then 0.0.0.0.0 = 07/30/-3061 G and 13.0.0.0.0 = 12/08/2064 G 622,243 then 0.0.0.0.0 = 07/17/-3009 G and 13.0.0.0.0 = 11/26/2116 G 641,223 then 0.0.0.0.0 = 07/05/-2957 G and 13.0.0.0.0 = 11/13/2168 G

To sum things up, people with a casual interest in the Mayan calendar will get by with a book or simpler Mayan calendar program. However those of us hardcores who live by the calendar will find the program indispensable.

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The software and documentation is in both English and in German.
Full documentation for the software is at
http://www.hermetic.ch/cal_sw/maya/mgc.htm
An explanation of the Maya Calendar is at
http://www.hermetic.ch/cal_stud/maya/cont.htm